The Stovebolt Site Forums The Shop Area Driveline 12 bolt rear end

Going to 3.73 from 4.11 is about a 9% improvement. The swap will be work and money. You'll need a driveshaft and a transmission with open drive design. Shock mounts and parking brake conversions will take time and work. When you're all done, the rpm needed to drive at 55 won't seem much different. 9% is not much. 3.55 however is about a 14% reduction in rpm at 55mph. So in the first example, you might reduce 3000 rpm to 2730. In the second example you might reduce 3000 rpm to 2580. If you're going with a 12 bolt rear (which I've done already) I would suggest looking into a T5 transmission. Then you can get some real flexibility with rpm, etc. and you're going to have to get a different transmission anyway. Good luck.